Grain size dependence of mobility in polycrystalline n-indium phosphide

Polycrystalline n-indium phosphide (InP) with grain sizes varying from 15 to 2000 μm has been prepared by iodine chemical reaction and synthesis solute diffusion (SSD) techniques. The variation of electron mobility and hence electron mean free path with grain size has been determined from conductivity and Hall effect studies, taking into account the effect of compensation as discussed by Jensen. The results show that electron mobility at 300 K increases from 29 to 691 cm2/V s with grain sizes increasing from 15 to 2000 μm. While for a single crystal the electron mobility varied with temperature between 160–300 K as T−2.25, for polycrystalline InP the variation was T−2.44 (2000 μm in grain size) and T−2.97 (200 μm in grain size) showing the effect of grain boundary scattering. The impurity activation energies have also been determined and were found to increase with a decrease of grain size.